Acidic ionic liquids are attractive as catalysts in many refinery and petrochemical process applications where the ionic liquid catalyst is easily mixed with the reactants in a reactor, followed by separation of the catalyst and hydrocarbon product in a settler. Ionic liquid catalysts are particularly useful for hydrocarbon conversion processes such as alkylation, olefin oligomerization, isomerization and disproportionation.
Conjunct polymers are by-products of the hydrocarbon reaction using ionic liquids, and they form a complex with the Lewis acid portion of the ionic liquid catalyst. The ionic liquid catalyst loses its effectiveness over time as the amount of conjunct polymer increases. The ionic liquid catalyst must then either be replaced or regenerated. Because ionic liquids are typically fairly expensive, processes for regenerating the ionic liquid catalysts are needed.
Ionic liquid catalyst can be regenerated by reacting with hydrogen gas in the presence of a solid hydrogenation catalyst under hydrogenation conditions (“hydro-regeneration”). Under hydro-regeneration process conditions, the conjunct polymers are liberated from the ionic liquid catalyst and cracked down to lighter molecules which are extracted downstream by solvent extraction and the regenerated ionic liquid catalyst recovers its activity.
Over the course of the hydro-regeneration process, the regeneration reactor occasionally suffers from pressure build-up primarily due to the formation of by-products that may ultimately result in undesirable process shut-down. Unwanted by-products may include corrosion product metals, gummy oligomers, cokes, and hydrolyzed solids formed as a consequence of trace water or polar hydrocarbons in the feed. It is believed that the pressure build-up is due to localized accumulation of these by-products on the external surface of the solid hydrogenation catalyst bed; this in turn creates higher flow resistance to the ionic liquid catalyst. Localized plugging of the solid hydrogenation catalyst may result in early termination of the regeneration process and a shortened catalyst life. There exists a need to extend hydro-regeneration catalyst life and improve reliability of the process.